The present disclosure relates to an acoustic liner and more particularly to an acoustic liner that extends noise attenuation capability to a lower frequency range.
A gas turbine engine may include an acoustic liner for attenuating noise generated during engine operation. A typical acoustic liner includes a honeycomb core connected between a solid face sheet and a perforated face sheet, also known as a single degree of freedom (SDOF), local reacting, liner. This honeycomb core includes a plurality of resonating cavities. The honeycomb core may have a height that tunes the resonating cavities to a specific target frequency of the noise to be attenuated.
New aircraft engine designs are facing increasing noise restrictions within the boundaries of airports by many government regulatory agencies. Accordingly, recent trends in aircraft engine design (i.e. higher bypass ratios, large fan diameter, slower rotating fans, and/or less fan blades) have highlighted the need for acoustic liners that provide sound suppression, such as tonal and broadband sound absorption at relatively low frequencies while utilizing substantially the same or less space than previous liners. Therefore, there is a need in the art for an improved noise attenuating acoustic panel with reduced acoustic liner thickness.